New modes of Doppler ultrasound and new signal conditioning of the received sonic specta permit accurate assessment of mean and peak velocities of intracardiac blood flow. Color encoded, two dimensional Doppler permits qualitative and quantitative evaluations of entire flow field velocity patterns. Studies utilizing these technologies include the following: (1) Quantitation of gradients in Newfoundland dogs with subaortic stenosis; (2) Comparison of ultrasound Doppler with laser Doppler anemometry; (3) Studies of intracardiac shunt flow; (4) Doppler color flow mapping of prosthetic mitral valves; and (5) Quantitation of obstruction and regurgitation in right ventricular to pulmonary arter conduits with and without prosthetic values. Studies in patients, both intraoperatively and postoperatively, have been initiated for the assessment of operations for valvular lesions and congenital cardiac defects.